The present invention relates to a method for improving the reliability of redundant protection circuits.
The growth of the market for small electronic devices has fueled developments on many fronts. The miniaturization of devices has found functions being performed on ever smaller and lighter devices. As the circuitry of electronic devices has continued to shrink, the need for circuit protection has grown. Over-voltage protection circuits exist to prevent damage to small devices and to the batteries that power them.
Over-voltage protection circuits are found in every sort of power supply, battery charging circuit, control circuitry and many others. The circuits are necessary to protect tiny electronic elements from the damage that excessive voltages and currents can cause.
Battery charging, in particular, can expose batteries to significant damage in the event of overcharging. This is especially true of high density rechargeable batteries such as Nickel-Cadmium (NiCd), Nickel-Metal Hydride (NiMH) and Lithium Ion (Li-Ion). Overcharging of Lithium Ion batteries also includes the additional risk of an explosive hazard.
High density batteries that are specially designed for a particular application can be expensive. Most users of cellular phones, for instance, cannot easily acquire spares. Loss of such batteries to damage from over-charging could be a crucial loss to in some situations. Even more crucial is the possible injury to a user from an overcharging explosion. Such loss must be prevented.
As a result, numerous protective circuits have been developed, and sometimes designed into the parent devices, to protect these batteries from overcharging. Many of the protective circuits used in more critical applications have redundant circuitry included in order to provide as much security as possible. However, current redundant circuits are merely copies of the primary circuit and some types of failures can cause a failure of redundancy. Merely adding more iterations of identical circuitry, too, adds unnecessary weight and complexity to a device.
What is needed then, is a means of providing multiple safeguards in redundant protective circuits that minimize common failure modes. Furthermore, such a means of protection must minimize additional weight, complexity and cost.
Embodiments of the present invention disclose a method for providing improved reliability of redundant protective circuits. The method provides improved reliability at a minimum penalty in weight, complexity and cost.
The present invention relates to a method for providing improved reliability in a protective circuit. Specifically, embodiments of the present invention provide improved reliability by coupling the outputs of functional elements of redundant protective circuits through OR gates to the inputs of subsequent functional elements. By this cross-coupling of individual circuit output signals between redundant circuit blocks, a failure of any functional element can be bypassed, allowing any non-failed functional element to supply the signal missing from a failed functional element.
More specifically, embodiments of the present invention disclose an electronic circuit capable of preventing over-voltage conditions in an electronic device. The circuit includes a first section and a second section, each capable of simultaneously performing the functions of both sections. The first and second sections are comprised of equivalent functional elements coupled in a fashion that enables the circumvention of any failed functional element without degradation of the functionality of the overall electronic circuit.